20090505

Multi-Qubit Quantum Coherent Operations College Park "The purpose of this meeting is to identify – on a technology-specific basis – the primary difficulties that are likely to be encountered as qubit systems beyond typical current experiments with one, two, or three qubits are pursued. Topics of interest include, but are not limited to: controllable qubit interactions, miniaturization and integration to increase qubit density, new physics arising from the assembly of many-qubit systems, and process and state validation for larger systems. The workshop aims to address the following questions:

Given a particular qubit technology that has already demonstrated full single qubit control, what are the challenges facing this system as it grows into the multiple qubit regime? In a system with multiple qubits, what will be the mechanism(s) through which these qubits interact? How can these interactions be well enough controlled to achieve reliable, scalable logic gates? Do they contribute to decoherent processes?

What new physics must be taken into account for the benefit of, or hindrance to, many qubit operations? Are there any fundamental results that will inform the community of possible roadblocks that may be encountered when growing systems to the multiple qubit regime?

How can cross-talk from the control/readout channel for one qubit, to a bystander qubit, be reduced to a satisfactory level? What are the specific technologies required to ensure that a robust multi-qubit information processing system can be realized?

As systems grow larger, quantum state and, and even more so, process tomography will become impractical. What other measures will be effective for validating the operations of these systems?"

“The United States … create a scientific foundation for controlling, manipulating, and exploiting the behavior of quantum matter, and for identifying the physical, mathematical, and computational capabilities and limitations of quantum information processing systems in order to build a knowledge base for this 21st century technology.”

This Workshop on Quantum Information Science (QIS) has been organized in response to the NSTC report. It brings together leading theorists and experimenters drawn from physical science, computer science, mathematics, and engineering who will assess recent progress in QIS and identify major goals and challenges for future research."

20090306

Density plot of qubit purityξ after t =20 kicks as a function of chaos parameter K=kT and nonlinear parameter g for T=2, δ=0.2 and ε=0.5.

Chaotic dynamics of a Bose-Einstein condensate coupled to a qubit Shepelyansky, Martin, Georgot arXiv 0812.5067: "We study the coupling between a qubit and a Bose-Einstein condensate moving in a kicked optical lattice. In the regime where BEC size is smaller than the lattice period, the chaotic dynamics of the BEC is effectively controlled by the qubit state. This gives an example of exponentially sensitive control over a macroscopic state by internal qubit states. The realization of such coupled systems is within reach of current experimental techniques."

Interference of interacting matter waves Innsbruck arXiv0812.4836:"The phenomenon of matter wave interference lies at the heart of quantum physics. It has been observed in various contexts in the limit of non-interacting particles as a single particle effect. Here we observe and control matter wave interference whose evolution is driven by interparticle interactions. In a multi-path matter wave interferometer, the macroscopic many-body wave function of an interacting atomic Bose-Einstein condensate develops a regular interference pattern, allowing us to detect and directly visualize the effect of interaction-induced phase shifts. We demonstrate control over the phase evolution by inhibiting interaction-induced dephasing, and by refocusing a dephased macroscopic matter wave in a spin-echo type experiment. Our results show that interactions in a many-body system lead to a surprisingly coherent evolution – possibly enabling narrow-band and high-brightness matter wave interferometers based on atom lasers."

20090226

Entanglement made VisibleGenève In arXiv 0902.2896 and arXivblogsummary, Gisinet al. show that macroscopic entanglement – and Bell inequality violations – can be made directly visible to the human retina. "We have shown that quantum experiments with human eyes as detectors appear possible, based on a realistic model of the eye as a photon detector. Entanglement, in principle, can be seen."

The Case for a National Investment: A Policy Essay for the Obama Transition Office In a recent CCC white paper, Aaronson and Bacon present the case for quantum computing as a national mandate. "First, quantum computing must be considered a national security issue. Since quantum computers break the codes used ubiquitously to protect transactions over the Internet, any country obtaining a scalable quantum computer would have the ability to disrupt electronic communication. Second, quantum information science research will help to maintain the US's scientific and technological advantages. Third, quantum computing is the study of the fundamental limits of computing and, as such, offers the potential to revolutionize our understanding of computation itself."

Pentagon explores quantum biologyDARPA/DSO has launched a research initiative to investigate quantum mechanical effects in biological systems [initial Wiredannouncement, Sep. 2008]. "Scientists have recently discovered that quantum energy transfers allow plants and cynobacteria to convert sunlight into chemical energy nearly instantly, and with almost 100 percent efficiency. As energy passes between molecules involved in photosynthesis, a newly-observed 'wavelike characteristic' allows the energy to 'simultaneously sample all the potential energy pathways and choose the most efficient one.' DARPA says there are other biological examples of quantum effects — including an explanation, perhaps, for how birds are able to navigate along the Earth's magnetic fields."

20090115

Quantum effects in biosystems Discover Magazine In Discover (February 2009), Mark Anderson reviews contemporary experiments in biophysics that explore the influence of quantum effects in living systems: "Could quantum mechanisms be driving some of the most elegant and inexplicable processes of life? For years experts doubted it: Quantum phenomena typically reveal themselves only in lab settings, in vacuum chambers chilled to near absolute zero. Biological systems are warm and wet. Most researchers thought the thermal noise of life would drown out any quantum weirdness that might rear its head. Yet new experiments keep finding quan­­tum processes at play in biological systems, says Christopher Altman, alumni researcher from European futurist think tank Starlab. With the advent of powerful new tools like femtosecond (10-15 second) lasers and nanoscale-precision positioning, life’s quantum dance is finally coming into view."

The Unmanned Air Force USAF In Network World and concurrent Slashdot updates, Lt. Gen. Seip discusses the future of unmanned combat aerial vehicles. "How important have unmanned aircraft become to the US military? Well, how's this: the Air Force says next year it will acquire more unmanned aircraft than manned aircraft. Air Force Lt. Gen. Norman Seip this week said the service is "all in" when it comes to developing unmanned systems and aircraft.' Next year, the Air Force will procure more unmanned aircraft than manned aircraft,' the general said. 'I think that makes a very pointed statement about our commitment to the future of unmanned aircraft, and what it brings to the fight in meeting the requirements of combatant commanders.'"